In the discussion of the background that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicants expressly reserve the right to demonstrate that such structures and/or methods do not qualify as prior art.
It is frequently desired to analyze a liquid to determine the presence and concentration of analytes such as minor constituents and/or contaminants. For instance, swimming pool water is tested frequently for various parameters, including alkalinity, pH, chlorine content, bromine content, water hardness and cyanuric acid, in order to maintain safe water for swimmers.
Chlorine is a disinfectant and an oxidizer. As a disinfectant, chlorine can kill bacteria and other microorganisms and helps control algae growth. Chlorine also oxidizes organic matter that might otherwise provide nutrients for microorganism growth. Oxidation of inorganic materials, pyrogens and metals by chlorine helps minimize staining and corrosion. Chlorine is the most widely used chemical for sanitizing and oxidizing pool water and spa water.
Chlorine in pool and spa water can be present in two forms. Free chlorine functions to kill microorganisms such as bacteria, and oxide contaminants. When free chlorine reacts with contaminants, it becomes combined chlorine. Combined chlorine has very little sanitizing ability and no oxidizing ability in pool or spa water. In addition, combined chlorine such as chloramines may cause eye irritation and may produce a chlorine odor that is unpleasant. Therefore, it is important to maintain a sufficient level of free chlorine for sanitization and oxidation in pool or spa water. It is also important to monitor the amount of combined chlorine to manage its presence appropriately.
Maintaining the appropriate level of free chlorine requires testing for free chlorine and total chlorine in pool water. Combined chlorine is calculated as the difference between total chlorine and free chlorine.
Current test kits for testing swimming pool water conventionally require the user to perform one test at a time, which can be time-consuming. Some currently available test kits use reagent solutions that are not stable or utilize a two-part reagent method. Other kits utilize tablets however the rate and complete dissolution of the tablets is problematic. An alternative type of kit utilizes test strips and test strip readers. Strip readers are fast and allow analysis of multiple analytes. However, they are far less accurate than conventional photometric analysis.
One of the most efficient kits currently available is WATERLINK™ 3 EXPRESS, manufactured by LaMotte Company (Chestertown, Md.). This is an in-store pool test system that comprises unit dose vials (UDV). Each vial contains a powdered reagent for a single parameter assessment. Activation of the UDV vials by addition of a sample of pool water is a manual process and is therefore vulnerable to potential operator error. Since multiple UDVs (containing different reagents) are necessary to assess various pool parameters, the testing process can be time consuming. In addition, manufacture of the UDV vials requires dry powdered reagents to be dispensed in each vial in the milligram range. Maintaining the uniformity of a dry powered reagent mixture can be difficult.
There is a need in the art for improved compositions to test an aqueous sample for total chlorine content.